1. Field of the Invention
The invention relates generally to the field of molecular biology. More specifically, it relates to nucleic acid sequences for the expression of recombinant nucleic acid sequences in transgenic cells and methods related thereto.
2. Description of the Related Art
An important aspect in the production of genetically engineered plants is obtaining sufficient levels of transgene expression in the appropriate plant tissues. In this respect, the selection of promoters for directing expression of a given transgene is crucial. Promoters which are useful for plant transgene expression include those that are inducible, viral, synthetic, and constitutive as described (Poszkowski et al., 1989; Odell et al., 1985).
A number of plant promoters have been described with various expression characteristics. Examples of some constitutive promoters which have been described include the rice actin 1 (Wang et al., 1992; U.S. Pat. No. 5,641,876), CaMV 35S (Odell et al., 1985), CaMV 19S (Lawton et al., 1987), Ti plasmid nopaline synthase (nos, Ebert et al., 1987), alcohol dehydrogenase (Adh, Walker et al., 1987), maize ubiquitin promoter (Christensen and Quail, 1996), and sucrose synthase promoters (Yang and Russell, 1990).
Examples of tissue specific promoters which have been described include the lectin (Vodkin et al., 1983; Lindstrom et al., 1990), corn alcohol dehydrogenase 1 (Vogel et al., 1989; Dennis et al., 1984), corn light harvesting complex (Simpson, 1986; Bansal et al., 1992), corn heat shock protein (Odell et al., 1985; Rochester et al., 1986), pea small subunit RuBP carboxylase (Poulsen et al., 1986; Cashmore et al., 1983), Ti plasmid mannopine synthase (Langridge et al., 1989), Ti plasmid nopaline synthase (Langridge et al., 1989), petunia chalcone isomerase (Van Tunen et al., 1988), bean glycine rich protein 1 (Keller et al., 1989), truncated CaMV 35s (Odell et al., 1985), potato patatin (Wenzler et al., 1989), root cell (Conkling et al., 1990), cab (Sullivan et al., 1989), PEPCase (Hudspeth and Grula, 1989), R gene complex-associated promoters (Chandler et al., 1989), and chalcone synthase promoters (Franken et al., 1991).
Inducible promoters which have been described include ABA- and turgor-inducible promoters, the promoter of the auxin-binding protein gene (Schwob et al., 1993), the UDP glucose flavonoid glycosyl-transferase gene promoter (Ralston et al., 1988); the MPI proteinase inhibitor promoter (Cordero et al., 1994), and the glyceraldehyde-3-phosphate dehydrogenase gene promoter (Kohler et al., 1995; Quigley et al., 1989; Martinez et al., 1989).
Both the CaMV 19S and 35S promoters have been used for constitutive expression of transgenes in plants. The 35S promoter is considered to be one of the strongest promoters in plants. (Guilley et al., 1982). The 35S promoter mediates expression of foreign genes in almost any organ of the plant and is the most commonly utilized promoter for the constitutive expression of any gene of interest in plants (Odell et al., 1985; Jefferson et al., 1987).
Although prior studies have provided a number of useful tools for the generation of transgenic plants, there is still a great need in the art for novel sequences that function as promoter elements for the high-level expression of transgenes. New promoters, especially promoters that will express transgenes at high levels, are needed. In addition to providing valuable new tools for the expression of transgenes, a wider range of effective promoters also would make it possible to introduce multiple transgenes into a cell while still avoiding the risk of DNA sequence homology dependent transgene inactivation. Therefore, there is a great need in the art for the identification of novel promoter elements for expression of transgenes in eukaryotes.